Pharmacopoeial Quality Standards for Radiopharmaceuticals for Positron-Emission Tomography

Pharmaceutical Chemistry Journal - The current state of quality standards for radiopharmaceuticals (RPs) for positron-emission tomography (PET) is assessed considering primarily national and global...     

Recognition molecule associated carbohydrate inhibits postsynaptic GABA(B) receptors: a mechanism for homeostatic regulation of GABA release in perisomatic synapses

Extracellular matrix molecules are important cues in the shaping of nervous system structure and function. Here, we describe a novel mechanism by which the HNK-1 carbohydrate carried by recognition molecules regulates perisomatic inhibition in the hippocampus. Neutralization of HNK-1 activity by an HNK-1 antibody results in GABA(B) receptor-mediated activation of K(+) currents in CA1 pyramidal cells, which elevates extracellular K(+) concentration and reduces evoked GABA release in perisomatic inhibitory synapses. This mechanism is supported by pharmacological analysis in hippocampal slices and data showing that the HNK-1 carbohydrate binds to GABA(B) receptors and inhibits GABA(B) receptor-activated K(+) currents in a heterologous expression system. We suggest that the HNK-1 carbohydrate is involved in homeostatic regulation of GABA(A) receptor-mediated perisomatic inhibition by suppression of postsynaptic GABA(B) receptor activity.     

Determining the kinetic characteristics of plant raw material extraction by repercolation

The kinetic laws of the plant-raw-material extraction process in pulsating equipment using a repercolation method have been studied. The rate of the extraction process was determined as a function of the temperature, concentration of extractable compounds, and the solid phase state. Conclusions are made concerning the possibility of using mathematical modeling for the calculation and optimization of commercial extraction processes.     

PTEN Contributes to Profound PI3K/Akt Signaling Pathway Deregulation in Dystrophin-Deficient Dog Muscle

Duchenne muscular dystrophy is the most common and severe form of muscular dystrophy, and although the genetic basis of this disease is well defined, the overall mechanisms that define its pathogenesis remain obscure. Alterations in individual signaling pathways have been described, but little information is available regarding their putative implications in Duchenne muscular dystrophy pathogenesis. Here, we studied the status of various major signaling pathways in the Golden Retriever muscular dystrophy dog that specifically reproduces the full spectrum of human pathology. Using antibody arrays, we found that Akt1, glycogen synthase kinase-3β (GSK3β), 70-kDa ribosomal protein S6 kinase (p70S6K), extracellular signal-regulated kinases 1/2, and p38δ and p38γ kinases all exhibited decreased phosphorylation in muscle from a 4-month-old animal with Golden Retriever muscular dystrophy, revealing a deep alteration of the phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinase pathways. Immunohistochemistry analysis revealed the presence of muscle fibers exhibiting a cytosolic accumulation of Akt1, GSK3β, and phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase (PTEN), an enzyme counteracting PI3K-mediated Akt activation. Enzymatic assays established that these alterations in phosphorylation and expression levels were associated with decreased Akt and increased GSK3β and PTEN activities. PTEN/GSK3β-positive fibers were also observed in muscle sections from 3- and 36-month-old animals, indicating long-term PI3K/Akt pathway alteration. Collectively, our data suggest that increased PTEN expression and activity play a central role in PI3K/Akt/GSK3β and p70S6K pathway modulation, which could exacerbate the consequences of dystrophin deficiency.Duchenne muscular dystrophy (DMD) is an X-linked neuromuscular disorder that affects 1 newborn boy in 3500. This recessive disease is caused by mutations in the dystrophin gene, resulting in total lack of the protein,^1,2,3 and is characterized by severe degeneration of muscle fibers, progressive paralysis, and death. Dystrophin is located under the sarcolemma of muscle fibers, and is associated with a complex comprising several integral, peripheral membrane and cytoplasmic proteins: the dystrophin-glycoprotein complex (DGC).^4,5,6,7 By providing a strong physical link between the cytoskeleton network and the extracellular matrix, the DGC ensures the integrity of skeletal muscle fibers. In the absence of dystrophin, the complex is destabilized and this integrity is lost.^5,8 However, the impaired structural role of the DGC alone may not be sufficient to account for the massive degenerative process observed in DMD muscles. Numerous observations suggest that signaling pathway alterations may also participate in DMD pathogenesis.Dystrophin and various DGC proteins have been demonstrated to interact with a number of signaling proteins, including growth factor receptor-bound protein 2,⁹ neuronal nitric oxide synthase,¹⁰ calmodulin,¹¹ focal adhesion kinase,¹² and caveolin-3.^13,14,15 Moreover, studies of the X chromosome-linked muscular dystrophy (mdx) mouse¹⁶ revealed modulations in mitogen-activated protein kinase (MAPK) signaling cascades, as dystrophic animals exhibited increased phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2)^17,18 and c-jun N-terminal kinases 1 and 2 (JNK1/2),^19,20,21 and decreased phosphorylation of p38.¹⁸ Also, the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway has been shown to be affected in the mdx mouse, with increased synthesis and phosphorylation of Akt.^22,23In addition to the limited information related to the origin of signal perturbations in dystrophic muscle, almost no information is available regarding signaling pathways in clinically relevant animal models or human tissue samples.²³ It is noteworthy that the mdx mouse model of DMD is characterized by successive degeneration/regeneration processes, but does not exhibit the progressive muscle wasting and accumulation of connective tissue observed during the development of the human disease.^24,25,26 The Golden Retriever muscular dystrophy (GRMD) dog, characterized by rapidly progressive clinical dysfunction, severe muscle weakness, and abundant fiber necrosis, displays a disease progression that is far more similar to human DMD.^27,28In this study, we used antibody arrays to assess the global phosphorylation status of key proteins of the PI3K/Akt and MAPK signaling pathways in skeletal muscles of 4-month-old healthy and GRMD dogs. Our data indicated that Akt1, glycogen synthase kinase-3β (GSK3β) and p70S6K, as well as ERK1/2 and p38δ and γ kinases all displayed a decreased phosphorylation level in GRMD muscle. Western immunoblot, immunohistochemistry analysis, and enzymatic assays allowed us to confirm these results and demonstrated that they were associated with a reduction in Akt activity and with enhanced GSK3β expression and activity. Analysis of key enzymes involved in Akt regulation revealed that phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase (PTEN) was present at a much higher level and was more active in GRMD muscle. Moreover, immunohistochemistry analysis showed that all of the GSK3β-positive fibers observed in GRMD muscle sections exhibited a strong cytosolic labeling of PTEN, suggesting that the accumulation of the phosphatase could play a central role in PI3K/Akt signaling pathway deregulation. The observation of PTEN/GSK3β-positive fibers in muscle sections from 3- and 36-month-old GRMD dogs further demonstrated that both the early and late stages of the disease share deregulation of the pathway. Collectively, our findings highly suggest that alterations in PTEN exist in GRMD muscle, which leads to long-term and deep modulation of the PI3K/Akt signaling pathway.     

Natural coumarins: Methods of isolation and analysis

With a view to optimizing of the quality control of sweetclover herbs and related preparations containing coumarins among the active substances, methods for the isolation and analysis of compounds of this class — in particular, coumarin and furocoumarin — are reviewed. The group of possible analytical methods includes gravimetric, titrimetric, photocolorimetric, and polarographic analysis, and the more recently developed spectroscopic (UV and IR), fluorimetric, and chromatographic (GC and HPLC) techniques. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 6, pp. 47–56, June, 2006.